The Population Dynamics Core will provide demographic information on the multicultural population of specific study areas, the region, state, and other contexts. The broad objective is to provide a longitudinal accounting of populations with rapidly changing composition and to locate specific ethnic groups in sufficient spatial detail to support localized sampling of different ethnic groups. Composition data will be specified by race-ethnicity, age, gender, immigration history (native-born or decade of immigrants' arrival), and other factors where appropriate. Specific aims include the following: organize demographic data sets for many sources (decennial census, Current Population Survey, the new American Community Survey, and others) to interface with existing and proposed surveys of tobacco use behavior; organize school-based data collected annually by race and by language of instruction for systematic linkage to 1990 and 2000 census data; prepare annual estimates of the small-area location of detailed ethnic groups of Asian or Latino heritage; prepare a population standardization matrix for adjustment of aggregate prevalence rates across time; and organize demographic data and tobacco and tobacco survey data in cohort format based on the 'double cohort' design for use with repeated surveys of immigrants and native borns.